1. Field of the Invention
The present invention relates to a coating apparatus which applies conductive liquid such as paste material to a predetermined area of a work.
2. Description of the Related Art
In manufacturing a flat panel display such as a liquid crystal display (LCD), a coating apparatus is used to apply a coat of conductive paste material for electrically connecting two liquid crystal substrates.
A coating apparatus 100 shown in FIG. 10 comprises a base unit 121, a container unit 122 which is supported movably up and down on the base unit 121, a pressure unit 125 which supplies compressed air to the inside of the container unit 122, and discharges paste material S from a discharge unit 123a provided at the front end of a container, a work support unit 127 which holds a work movably, an upthrust mechanism 128 which moves up and separates a substrate from the work support unit 127 when changing a work, and a control unit 130 which controls operations of the component units. The base unit 121 is grounded.
The coating apparatus 100 moves and positions the work support unit 127 in two directions of X and Y axes, so that the discharge unit 123a is set directly above a required position (a coating area) on a substrate.
A coating area becomes an electrical circuit 112a to be formed on the substrate 112, for example. The container unit 122 is moved down in the state in which the discharge unit 123a is opposed to the substrate 112, and the distance from the discharge unit 123a to the substrate 112 is set to a required value.
In this state, the pressure unit 125 supplies compressed air to the container unit 122, and the discharge unit 123a discharges the paste material S. One coating cycle is completed by the above operations.
After coating a required area, the container unit 122 is moved up, and the substrate 112 is moved to the next position. A plurality of areas of the substrate are coated by repeating this step (refer to Jpn. Pat. Appln. KOKAI Publication No. 2006-153971, for example).
When the coating operation required for one substrate 112 is finished, the upthrust mechanism 128 is operated, the substrate 112 is moved up from the work support unit 127, and replaced by another substrate, and the same coating operation is repeated for the new substrate as the next coating object. The above operations are repeated for coating a plurality of substrates 112.
However, the above technique has the following problems. Each time a coating operation is repeated, a discharge unit or paste material contacts and separates from a substrate or an electrical circuit. Electric charge is transferred by the repetition of contacting and separation. As the base unit is grounded, electric charge is imparted at every coating operation. Therefore, a substrate is electrically charged if the coating operation is repeated.